String for a racket

ABSTRACT

A string for a racket includes: a first part including a first core and a first sheath layer molded over the first core; a second part including a plurality of reinforcing strips disposed side by side around and twisted about the first sheath layer of the first part, each of the reinforcing strips having a second core and a second sheath layer molded over the second core; and an outer sheathing layer sheathing the second part. The first core and the first sheath layer of the first part, the second core and the second sheath layer of each of the reinforcing strips of the second part, and the outer sheathing layer are made from a material selected from an elastic material and a hardened material.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a string for a racket, more particularly to a string having a structure that is capable of providing good wear-resistance, elasticity, and mechanical strength to a racket.

2. Description of the Related Art

FIGS. 1 and 2 show a conventional string 10 for a racket and an extruder 20 for preparing the same (only a die unit of the extruder 20 is shown in FIG. 2). The conventional string 10 includes a toothed core 11 made of a first plastic material, and a sheath layer 12 made of a second plastic material and molded over the toothed core 11. As shown in FIG. 2, the string 10 is prepared by co-extruding the first plastic material 120 from a first flow passageway 21 of the extruder 20 and the second plastic material 110 from a second flow passageway 22 of the extruder 20. Since the first plastic material 120 has a hardness and a wear-resistance less than those of the second plastic material 110, the structure thus formed can provide the string 10 with good elasticity and wear-resistance. FIG. 3 shows a modified string 30 which includes a first part 10 having a core and a sheath layer, a fiber unit including two fiber layers 31, each of which has a plurality of fibers arranged side by side around and twisted about the sheath layer of the first part 10, and an outer layer 32 covering the fiber unit.

Although the aforesaid strings 10, 30 exhibit good elasticity and wear-resistance, there is still a need in the art for a string having superior elasticity and wear-resistance.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide a string that has a structure capable of providing excellent wear-resistance, elasticity, and mechanical strength.

According to this invention, a string for a racket comprises: a first part including a first core and a first sheath layer molded over the first core; a second part including a plurality of reinforcing strips disposed side by side around and twisted about the first sheath layer of the first part, each of the reinforcing strips having a second core and a second sheath layer molded over the second core; and an outer sheathing layer sheathing the second part. The first core and the first sheath layer of the first part, the second core and the second sheath layer of each of the reinforcing strips of the second part, and the outer sheathing layer are made from a material selected from the group consisting of: an elastic material selected from the group consisting of thermoplastic polyurethane, thermoplastic polyester elastomer, thermoplastic styrene elastomer, polyamide elastomer, and combinations thereof; and a hardened material selected from the group consisting of Nylon 6, Nylon 66, polyethylene terephthalate, and combinations thereof. At least one of the first core and the first sheath layer of the first part, the second core and the second sheath layer of each of the reinforcing strips of the second part, and the outer sheathing layer is made from one of the elastic material and the hardened material, and the remainder are made from the other of the elastic material and the hardened material.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment of this invention, with reference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional view to illustrate a conventional string for a racket;

FIG. 2 is a fragmentary cross-sectional side view to illustrate formation of the conventional string of FIG. 1 via an extruder;

FIG. 3 is a perspective view of a segment of another conventional string;

FIG. 4 is a perspective view of a segment of a string embodying the present invention;

FIG. 5 is a cross-sectional view of the string of FIG. 4 taken along line V-V of FIG. 4; and

FIG. 6 is a schematic view of a racket having a cord netting of the string of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 4 and 5, the preferred embodiment of a string 4 for a racket according to the present invention is shown to include: a first part 40 including a first core 41 and a first sheath layer 42 molded over the first core 41; a second part 50 including a plurality of reinforcing strips 51 disposed side by side around and twisted about the first sheath layer 42 of the first part 40, each of the reinforcing strips 51 having a second core 52 and a second sheath layer 53 molded over the second core 52; and an outer sheathing layer 60 sheathing the second part 50.

The first core 41 and the first sheath layer 42 of the first part 40, the second core 52 and the second sheath layer 53 of each of the reinforcing strips 51 of the second part 50, and the outer sheathing layer 60 are made from a material selected from the group consisting of: an elastic material selected from the group consisting of thermoplastic polyurethane, thermoplastic polyester elastomer, thermoplastic styrene elastomer, polyamide elastomer (e.g., Nylon 12 elastomer), and combinations thereof; and a hardened material selected from the group consisting of Nylon 6, Nylon 66, polyethylene terephthalate, and combinations thereof. Preferably, at least one of the first core 41 and the first sheath layer 42 of the first part 40, the second core 52 and the second sheath layer 53 of each of the reinforcing strips 51 of the second part 50, and the outer sheathing layer 60 is made from one of the elastic material and the hardened material, and the remainder are made from the other material.

In this embodiment, the first core 41 of the first part 40 and the second core 52 of each of the reinforcing strips. 51 of the second part 50 are made from the elastic material, and the first sheath layer 42 of the first part 40, the second sheath layer 53 of the second part 50, and the outer sheathing layer 60 are made from the hardened material.

In this invention, the string 4 further includes an adhesive layer 70 filling a gap defined by the first and second sheath layers 42, 53, and the outer sheathing layer 60 (see FIGS. 4 and 5) for fixing the reinforcing strips 51 of the second part 50 in the gap so as to increase bonding strength between the outer sheathing layer 60 and the first sheath layer 42 of the first part 40 and to provide mechanical strength to a sport racket 8 (see FIG. 6).

By virtue of the structure of the second part 50, the wear-resistance, elasticity, and mechanical strength of the string 4 of this invention can be further enhanced as compared to the aforesaid conventional strings 10, 30.

While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation and equivalent arrangements. 

1. A string for a racket, comprising: a first part including a first core and a first sheath layer molded over said first core; a second part including a plurality of reinforcing strips disposed side by side around and twisted about said first sheath layer of said first part, each of said reinforcing strips having a second core and a second sheath layer molded over said second core; and an outer sheathing layer sheathing said second part; wherein said first core and said first sheath layer of said first part, said second core and said second sheath layer of each of said reinforcing strips of said second part, and said outer sheathing layer are made from a material selected from the group consisting of: an elastic material selected from the group consisting of thermoplastic polyurethane, thermoplastic polyester elastomer, thermoplastic styreneelastomer, polyamideelastomer, and combinations thereof; and a hardened material selected from the group consisting of Nylon 6, Nylon 66, polyethylene terephthalate, and combinations thereof; and wherein at least one of said first core and said first sheath layer of said first part, said second core and said second sheath layer of each of said reinforcing strips of said second part, and said outer sheathing layer is made from one of said elastic material and said hardened material, and the remainder are made from the other of said elastic material and said hardened material.
 2. The string of claim 1, wherein said first sheath layer, said second sheath layer, and said outer sheathing layer cooperatively define a gap thereamong, said string further comprising an adhesive layer filling said gap for fixing said reinforcing strips of said second part in said gap.
 3. The string of claim 1, wherein said first core of said first part and said second core of said second part are made from said elastic material, said first sheath layer of said first part, said second sheath layer of said second part, and said outer sheathing layer being made from said hardened material. 